Wall Street investors are nursing heavy losses on Bitcoin-linked investments as the first monthly futures contracts expire.One-month Bitcoin futures, which traded at close to $20,000 (£14,700) several weeks ago, have slumped in recent weeks as the cryptocurrency gold rush appears to fade. Bitcoin futures contracts launched on the Chicago Board Options Exchange (CBOE) in mid-December.It was seen as the moment that the cryptocurrency gained legitimacy among professional investors, allowing them to get a slice of the booming market for digital currencies with a regulated financial product, instead of buying Bitcoin directly. However, Bitcoin’s entry into the mainstream has coincided with a sharp dip in its price.